Screwdrivers and other hand-held tools are often utilized to insert, remove and/or adjust fasteners attached to various items. The tool is used to rotate the fasteners into or out of apertures in the items to properly position the fasteners with respect to the items.
In order to make the rotation of the fasteners easier when utilizing these tools, the tools often include ratcheting mechanisms which enable the tool to apply a force to the fastener when the tool is rotated in one direction, and to allow the tool to rotate freely without applying a force to the fastener in the opposite direction. Ratcheting mechanisms of this type take various forms, such as those disclosed in U.S. Pat. Nos. 5,613,585; 5,619,891; 5,778,743; 5,873,288; and 5,943,755. In each of these mechanisms, a pair of pawls are disposed within a housing for the tool. The pawls can be selectively engaged and disengaged from a toothed gear disposed within the tool housing in order to enable the gear to rotate in a specified direction to achieve the desired mechanical advantage when adjusting, inserting or removing a fastener.
However, while tools incorporating ratcheting mechanisms of this type are useful in adjusting, inserting and removing fasteners from various items, the mechanisms also have certain drawbacks. For example, due to the shape of the pawls and the corresponding placement of the pawls within the housing, prior art ratcheting mechanism constructions are unable to handle large amounts of torque without the teeth on the gear slipping past the pawls. Thus, for fasteners that are very tightly engaged with an item, mechanisms of this type effectively cannot be used to adjust, insert or remove the fasteners. Additionally, due to the large size and consequent spacing of the teeth on the gear, the tool must be rotated more than approximately 10° in order to advance the ratcheting mechanism to the next locking position. In situations where precise movements of a fastener are necessary, the tools incorporating mechanisms of the above-referenced type with gears of this size are not suitable as these mechanisms are very “coarse” and do not allow for precise movements of the fastener. Further, the prior art ratcheting mechanisms require a large number of parts to be assembled within the housing in order to complete the ratcheting mechanism, increasing the time and expense necessary for manufacturing tools incorporating these prior art ratcheting mechanisms.
Therefore, it is desirable to develop a ratcheting mechanism for hand- held tools that has a simple and easy to assemble construction, and that also provides the tool with the ability to easily and precisely adjust the position of a fastener on an item, no matter how securely the fastener is engaged with the item.